ARGENTINA represent the mirror in which Ireland get to see a true reflection of themselves, according to David Wallace.
And, for relative newcomers to the international scene like Peter O'Mahony, there is nothing that can adequately prepare them for what will likely be the toughest and most attritional Test match they will ever experience.
"There is no tougher or more physical match than one against Argentina," Wallace said.
"They are truly unforgiving. And there's always something at stake when we meet them, which adds to the occasion and the aggressive nature of the games.
"If anything, they are even more impressive this time around because they have added more to their game behind the pack.
"After this game we will have a true picture of where we are as a team."
O'Mahony is one of a new breed of Irish warriors coming through to the senior team and, while Wallace was hugely impressed with the progress of the 23-year-old last season, he believes he is even better now.
"Peter is a hugely physical and confrontational player. He never takes a step back and is, for want of a better description, an enforcer. He was very impressive in that role last season but he has evolved his game and is even more impressive this season," Wallace said.
"Where he has improved is in adding a lot of finesse to his game. We know he wants to go through people if possible – and he actually has the strength to do so as we saw against South Africa – but he can now go around them too.
"He has added that string to his bow and will, I believe, develop into a top-class blindside flanker."
O'Mahony is practically salivating at the prospect of going head to head with Argentina's back-row. He has no hesitation in admitting that he was a keen student of them during their inaugural season in the Rugby Championship.
This is a battle he will relish, as evident by his name-checking of two of their more aggressive enforcers in Juan Martin Fernandez Lobbe and Juan Manuel Leguizamon. And Wallace has absolutely no fears about the 23-year-old's ability to step up.
"Peter always lays his body on the line," said the former Munster and Ireland flanker.
"He is an immensely strong player, even more so than people might realise. His scores in the gym are phenomenal and the way he has grown as a player over the past season has been hugely impressive.
"Last season it was this raw talent that took everyone by surprise. Now you can see teams are singling him out as a dangerman, but he's still putting in carries, making hits and is clearly robust enough to take all the punishment that comes with back-row play."
O'Mahony is one of those anomalies that come along every so often – an experienced head on a young man's body. He is a former Munster schools and underage captain, and his potential was evident when Tony McGahan, then Munster coach, promoted him to captain in the absence of Paul O'Connell.
It was a remarkable show of faith in a young player, especially as there were more experienced campaigners in the squad.
Since that fillip to his confidence he has gone on to establish himself as one of Ireland's go-to players. At full tilt and in possession he is harder to stop than a toppling red oak and no less devastating.
He has what one more experienced Munster team-mate describes as "the Paul O'Connell psycho eyes" and thrives in the ultra-physical world of international rugby where only the very strongest survive.
That he hugely admires the Argentina players is not in doubt. He's particularly effusive in his praise of their work-ethic and how they dominate the crucial area of the breakdown.
"That's where rugby games are won. From one to 15, Argentina are hugely effective at the breakdown. They invariably get to the ball first and dominate from that position, which is what we have to be conscious of," he said.
"As a 15, we're going to have to front up here especially. It's as much a backs issue as it is a forwards issue these days.
"Their results didn't properly reflect how good they were during the Rugby Championship and they have come on a ton as a result of being involved."
So prominent has O'Mahony been for Munster and Ireland since breaking onto the scene at the start of last season that it is easily forgotten just how new these experiences are to him.
"I'm enjoying the experience. I don't know about this 'transition' thing to be honest. All teams have younger fellas constantly coming through and that's what's happening with Ireland and Munster at the moment," he said.
"Personally, there isn't a bigger honour than to be selected for your country and this is a great squad to be involved with.
"This weekend will be an absolutely huge test. We had a video analysis session and it's obvious just how good Argentina are.
"But the emphasis for us must be on ourselves and what we can do to help ourselves."